From 9fb02a70d0da161f7c3d8f98578e8fa19c4a09d0 Mon Sep 17 00:00:00 2001
From: Bryan Drewery <bdrewery@FreeBSD.org>
Date: Fri, 19 Feb 2016 00:41:24 +0000
Subject: [PATCH] Avoid reading .depend.* in simple cases where not needed.

This will speed up some tree-walks with FAST_DEPEND which otherwise
would include length(SRCS) .depend files.

This also uses a trick suggested by sjg@ to still read them in when
specifying _V_READ_DEPEND=1 in the env/make args.

Sponsored by:	EMC / Isilon Storage Division
---
 share/mk/bsd.dep.mk   | 12 +++++++++++-
 sys/conf/kern.post.mk | 11 ++++++++++-
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/share/mk/bsd.dep.mk b/share/mk/bsd.dep.mk
index 99fc9725774..6f27d7e117e 100644
--- a/share/mk/bsd.dep.mk
+++ b/share/mk/bsd.dep.mk
@@ -81,6 +81,16 @@ tags: ${SRCS}
 .endif
 .endif
 
+# Skip reading .depend when not needed to speed up tree-walks
+# and simple lookups.
+.if !empty(.MAKEFLAGS:M-V${_V_READ_DEPEND}) || make(obj) || make(clean*) || \
+    make(install*)
+_SKIP_READ_DEPEND=	1
+.if ${MK_DIRDEPS_BUILD} == "no"
+.MAKE.DEPENDFILE=	/dev/null
+.endif
+.endif
+
 .if defined(SRCS)
 CLEANFILES?=
 
@@ -181,7 +191,7 @@ DEPENDSRCS=	${SRCS:M*.[cSC]} ${SRCS:M*.cxx} ${SRCS:M*.cpp} ${SRCS:M*.cc}
 DEPENDOBJS+=	${DEPENDSRCS:R:S,$,.o,}
 .endif
 DEPENDFILES_OBJS=	${DEPENDOBJS:O:u:${DEPEND_FILTER}:C/^/${DEPENDFILE}./}
-.if ${.MAKEFLAGS:M-V} == ""
+.if !defined(_SKIP_READ_DEPEND)
 .for __depend_obj in ${DEPENDFILES_OBJS}
 .sinclude "${__depend_obj}"
 .endfor
diff --git a/sys/conf/kern.post.mk b/sys/conf/kern.post.mk
index 52cd186a13f..8983467b496 100644
--- a/sys/conf/kern.post.mk
+++ b/sys/conf/kern.post.mk
@@ -206,6 +206,15 @@ CFILES_OFED=${CFILES:M*/ofed/*}
 # We have "special" -I include paths for MLX5.
 CFILES_MLX5=${CFILES:M*/dev/mlx5/*}
 
+# Skip reading .depend when not needed to speed up tree-walks
+# and simple lookups.
+.if !empty(.MAKEFLAGS:M-V${_V_READ_DEPEND}) || make(obj) || make(clean*) || \
+    make(install*) || make(kernel-obj) || make(kernel-clean*) || \
+    make(kernel-install*)
+_SKIP_READ_DEPEND=	1
+.MAKE.DEPENDFILE=	/dev/null
+.endif
+
 kernel-depend: .depend
 # The argument list can be very long, so use make -V and xargs to
 # pass it to mkdep.
@@ -222,7 +231,7 @@ DEPEND_CFLAGS+=	-MT${.TARGET}
 CFLAGS+=	${DEPEND_CFLAGS}
 DEPENDOBJS+=	${SYSTEM_OBJS} genassym.o
 DEPENDFILES_OBJS=	${DEPENDOBJS:O:u:C/^/.depend./}
-.if ${.MAKEFLAGS:M-V} == ""
+.if !defined(_SKIP_READ_DEPEND)
 .for __depend_obj in ${DEPENDFILES_OBJS}
 .sinclude "${__depend_obj}"
 .endfor